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arXiv 1602.08730cs.DS
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图割与网络可靠性的改进界与算法

Improved bounds and algorithms for graph cuts and network reliability

David G. Harris, Aravind Srinivasan

AI总结:

本文通过改进Karger算法中子问题的估计和图参数界,将网络可靠性估计的运行时间从n^{5+o(1)} ε^{-3}降至n^{3+o(1)} ε^{-2},并严格证明了Karger & Tai的实验观察,同时改进了小割数量的界。

摘要:

Karger(SIAM Journal on Computing, 1999)提出了第一个全多项式近似方案,用于估计在给定边以概率p独立移除的情况下,图G变得不连通的概率。该算法运行时间为n^{5+o(1)} ε^{-3},以获得相对误差ε内的估计。我们通过算法和图论方面的进展改进了这一运行时间。首先,Karger遇到某个关键子问题,其中采用了一般的估计过程,我们表明该问题具有特殊结构,可以使用更高效的算法。其次,我们证明了可能失效的边割数量的更好界。这里,Karger的分析使用了各种图参数的多种界,我们表明这些界不能同时紧。我们描述了一个新的图参数,它同时影响Karger使用的所有界,并获得对G的割结构的更紧估计。这些技术使我们能够将运行时间改进到n^{3+o(1)} ε^{-2},我们的结果也严格证明了Karger & Tai(Proc. ACM-SIAM Symposium on Discrete Algorithms, 1997)的某些实验观察。我们的严格证明受到某些非严格的微分方程近似的启发,这些近似可证明地跟踪相关参数的最坏情况轨迹。Karger方法(以及其他割相关结果)的一个关键驱动因素是小割数量的界:当最小割大小“小”且为奇数时,我们改进了这些估计,部分增强了Bixby(Bulletin of the AMS, 1974)的一个结果。

英文摘要:

Karger (SIAM Journal on Computing, 1999) developed the first fully-polynomial approximation scheme to estimate the probability that a graph $G$ becomes disconnected, given that its edges are removed independently with probability $p$. This algorithm runs in $n^{5+o(1)} ε^{-3}$ time to obtain an estimate within relative error $ε$. We improve this run-time through algorithmic and graph-theoretic advances. First, there is a certain key sub-problem encountered by Karger, for which a generic estimation procedure is employed, we show that this has a special structure for which a much more efficient algorithm can be used. Second, we show better bounds on the number of edge cuts which are likely to fail. Here, Karger's analysis uses a variety of bounds for various graph parameters, we show that these bounds cannot be simultaneously tight. We describe a new graph parameter, which simultaneously influences all the bounds used by Karger, and obtain much tighter estimates of the cut structure of $G$. These techniques allow us to improve the runtime to $n^{3+o(1)} ε^{-2}$, our results also rigorously prove certain experimental observations of Karger & Tai (Proc. ACM-SIAM Symposium on Discrete Algorithms, 1997). Our rigorous proofs are motivated by certain non-rigorous differential-equation approximations which, however, provably track the worst-case trajectories of the relevant parameters. A key driver of Karger's approach (and other cut-related results) is a bound on the number of small cuts: we improve these estimates when the min-cut size is "small" and odd, augmenting, in part, a result of Bixby (Bulletin of the AMS, 1974).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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